B_INUSE
fbp->b_flags &= ~B_INUSE;
bp->b_flags &= ~B_INUSE;
bp->b_flags &= ~B_INUSE;
bp->b_flags &= ~B_INUSE;
bp->b_flags &= ~B_INUSE;
if ((bp->b_flags & B_INUSE) == 0)
bp->b_flags |= B_INUSE;
if ((bp->b_flags & B_INUSE) == 0)
bp->b_flags |= B_INUSE;
bp->b_flags &= ~B_INUSE;